One-Fifth of the World's Corals Are Dead: Climate Change to Blame

The main climate threats, such as increasing sea surface temperatures and ocean acidification, are compounded by other threats - overfishing, pollution and invasive species.

The report, released by the Global Coral Reef Monitoring Network based in Townsville, shows if current trends in carbon dioxide emissions continue, many of the remaining reefs may be lost over the next 20 to 40 years. This will affect some 500 million people who depend on coral reefs for their livelihoods.

"The report details the strong scientific consensus that climate change must be limited to the absolute minimum. If nothing is done to substantially cut emissions, we could effectively lose coral reefs as we know them, with major coral extinctions," says Clive Wilkinson, coordinator of the Global Coral Reef Monitoring Network.

The report shows that 45 percent of the world's reefs are currently healthy. Another sign of hope is the ability of some corals to recover after major bleaching events, caused by warming waters, and to adapt to climate change threats.

However, the report shows that, globally, the downward trend of recent years has not been reversed.

Major threats in the last four years, including the Indian Ocean tsunami, more occurances of bleaching, outbreaks of coral diseases and ever-heavier human pressures, have slowed or reversed recovery of some coral reefs after the 1998 mass bleaching event.

Coral bleaching at Yonehara reef in Ishigaki, Japan (Photo by Dan Kitchens)

"If nothing changes, we are looking at a doubling of atmospheric carbon dioxide in less than 50 years," says Carl Gustaf Lundin, head of the IUCN Global Marine Programme, one of the organizations behind the Global Coral Reef Monitoring Network.

"As this carbon is absorbed, the oceans will become more acidic, which is seriously damaging a wide range of marine life from corals to plankton communities and from lobsters to seagrasses," Lundin said.

Corals have a higher chance of survival in times of climate change if other stress factors related to human activity are minimized. Well-managed marine protected areas can also boost the health of coral reefs, but proper enforcement is difficult, especially in remote areas where the most pristine reefs are found.

"Ten years after the world's biggest coral bleaching event, we know that reefs can recover given the chance. Unfortunately, impacts on the scale of 1998 will reoccur in the near future, and there's no time to lose if we want to give reefs and people a chance to suffer as little as possible," says Dr. David Obura, chair of the IUCN Climate Change and Coral Reefs working group and director of the Coastal Oceans Research and Development in the Indian Ocean Programme, CORDIO, in East Africa.

A new report on the state of Indian Ocean coral reefs, launched today by CORDIO, an organization aligned with the Global Coral Reef Monitoring Network, reveals an overall trend of continued degradation, with signs of recovery in some areas.

"With this report, the far-reaching degradation of Indian Ocean coral reefs has become evident," says Olof Linden of the CORDIO network and professor at the World Maritime University, Malmo, Sweden. "To save coral reefs, we must focus on helping corals to adapt to climate change and on diverting people away from destructive practices such as overfishing."

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